/* SPDX-License-Identifier: BSD-2-Clause */

/**
 * @file
 *
 * @ingroup RTEMSScoreScheduler
 *
 * @brief This header file provides interfaces of the
 *   @ref RTEMSScoreScheduler related to scheduler nodes which are used by the
 *   implementation and the @ref RTEMSImplApplConfig.
 */

/*
 * Copyright (c) 2014, 2016 embedded brains GmbH.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef _RTEMS_SCORE_SCHEDULERNODE_H
#define _RTEMS_SCORE_SCHEDULERNODE_H

#include <rtems/score/basedefs.h>
#include <rtems/score/chain.h>
#include <rtems/score/priority.h>
#include <rtems/score/isrlock.h>

/**
 * @addtogroup RTEMSScoreScheduler
 *
 * @{
 */

struct _Thread_Control;

#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */

#if defined(RTEMS_SMP)
/**
 * @brief The scheduler node requests.
 */
typedef enum {
  /**
   * @brief The scheduler node is not on the list of pending requests.
   */
  SCHEDULER_NODE_REQUEST_NOT_PENDING,

  /**
   * @brief There is a pending scheduler node request to add this scheduler
   * node to the Thread_Control::Scheduler::Scheduler_nodes chain.
   */
  SCHEDULER_NODE_REQUEST_ADD,

  /**
   * @brief There is a pending scheduler node request to remove this scheduler
   * node from the Thread_Control::Scheduler::Scheduler_nodes chain.
   */
  SCHEDULER_NODE_REQUEST_REMOVE,

  /**
   * @brief The scheduler node is on the list of pending requests, but nothing
   * should change.
   */
  SCHEDULER_NODE_REQUEST_NOTHING,

} Scheduler_Node_request;
#endif

typedef struct Scheduler_Node Scheduler_Node;

/**
 * @brief Scheduler node for per-thread data.
 */
struct Scheduler_Node {
#if defined(RTEMS_SMP)
  /**
   * @brief Chain node for usage in various scheduler data structures.
   *
   * Strictly, this is the wrong place for this field since the data structures
   * to manage scheduler nodes belong to the particular scheduler
   * implementation.  Currently, all SMP scheduler implementations use chains
   * or red-black trees.  The node is here to simplify things, just like the
   * object node in the thread control block.
   */
  union {
    Chain_Node Chain;
    RBTree_Node RBTree;
  } Node;

  /**
   * @brief The sticky level determines if this scheduler node should use an
   * idle thread in case this node is scheduled and the owner thread is
   * blocked.
   */
  int sticky_level;

  /**
   * @brief The thread using this node.
   *
   * This is either the owner or an idle thread.
   */
  struct _Thread_Control *user;

  /**
   * @brief The idle thread claimed by this node in case the sticky level is
   * greater than zero and the thread is block or is scheduled on another
   * scheduler instance.
   *
   * This is necessary to ensure the priority ceiling protocols work across
   * scheduler boundaries.
   */
  struct _Thread_Control *idle;
#endif

  /**
   * @brief The thread owning this node.
   */
  struct _Thread_Control *owner;

#if defined(RTEMS_SMP)
  /**
   * @brief Block to register and manage this scheduler node in the thread
   * control block of the owner of this scheduler node.
   */
  struct {
    /**
     * @brief Node to add this scheduler node to
     * Thread_Control::Scheduler::Wait_nodes.
     */
    Chain_Node Wait_node;

    /**
     * @brief Node to add this scheduler node to
     * Thread_Control::Scheduler::Scheduler_nodes or a temporary remove list.
     */
    union {
      /**
       * @brief The node for Thread_Control::Scheduler::Scheduler_nodes.
       */
      Chain_Node Chain;

      /**
       * @brief The next pointer for a temporary remove list.
       *
       * @see _Thread_Scheduler_process_requests().
       */
      Scheduler_Node *next;
    } Scheduler_node;

    /**
     * @brief Link to the next scheduler node in the
     * Thread_Control::Scheduler::requests list.
     */
    Scheduler_Node *next_request;

    /**
     * @brief The current scheduler node request.
     */
    Scheduler_Node_request request;
  } Thread;
#endif

  /**
   * @brief Thread wait support block.
   */
  struct {
    Priority_Aggregation Priority;
  } Wait;

  /**
   * @brief The thread priority information used by the scheduler.
   *
   * The thread priority is manifest in two independent areas.  One area is the
   * user visible thread priority along with a potential thread queue.  The
   * other is the scheduler.  During a thread priority change, the user visible
   * thread priority and the thread queue are first updated and the thread
   * priority value here is changed.  Once this is done the scheduler is
   * notified via the update priority operation, so that it can update its
   * internal state and honour a new thread priority value.
   */
  struct {
    /**
     * @brief The thread priority value of this scheduler node.
     *
     * The producer of this value is _Thread_Change_priority().  The consumer
     * is the scheduler via the unblock and update priority operations.
     *
     * This priority control consists of two parts.  One part is the plain
     * priority value (most-significant 63 bits).  The other part is the
     * least-significant bit which indicates if the thread should be appended
     * (bit set) or prepended (bit cleared) to its priority group, see
     * SCHEDULER_PRIORITY_APPEND().
     *
     * @see _Scheduler_Node_get_priority() and _Scheduler_Node_set_priority().
     */
#if defined(RTEMS_SMP) && CPU_SIZEOF_POINTER == 8
    Atomic_Ulong value;
#else
    Priority_Control value;
#endif

#if defined(RTEMS_SMP) && CPU_SIZEOF_POINTER != 8
    /**
     * @brief The lock protects the priority value.
     */
    ISR_lock_Control Lock;
#endif
  } Priority;
};

#if defined(RTEMS_SMP)
/**
 * @brief The size of a scheduler node.
 *
 * This value is provided via <rtems/confdefs.h>.
 */
extern const size_t _Scheduler_Node_size;
#endif

#if defined(RTEMS_SMP)
#define SCHEDULER_NODE_OF_THREAD_WAIT_NODE( node ) \
  RTEMS_CONTAINER_OF( node, Scheduler_Node, Thread.Wait_node )

#define SCHEDULER_NODE_OF_THREAD_SCHEDULER_NODE( node ) \
  RTEMS_CONTAINER_OF( node, Scheduler_Node, Thread.Scheduler_node.Chain )
#endif

#ifdef __cplusplus
}
#endif /* __cplusplus */

/** @} */

#endif /* _RTEMS_SCORE_SCHEDULERNODE_H */
